Prescription Refill Calculator — When to Refill Your Medication
Enter your prescription quantity, daily dose and fill date to see how many pills you have left, when you will run out, and when to contact your pharmacy or doctor for a refill.
Prescription fill date
Today's date
days
16 days of supply remaining
- 1
Days supply
30 ÷ 1 = 30 - 2
Days elapsed since fill
14Calendar days between fill date and today. - 3
Pills used
14 × 1 = 14 - 4
Pills remaining
30 − 14 = 16
How does this calculator work?
Days supply = pills ÷ doses per day. Add that to your fill date for the run-out date; subtract your lead time for the refill-request date. Pills left today = total pills − (days elapsed × daily dose). Request your refill at least 7 days before running out to avoid a gap.
Formula
How this is calculated
The days-supply is simply the total number of tablets or capsules divided by the number of doses you take per day. A 30-pill prescription taken once daily gives 30 days; the same bottle taken twice daily gives only 15 days. The calculator adds that supply in days to the fill date to find the run-out date, then subtracts the lead time to find the target refill-request date — the last safe day to call the pharmacy without risking a gap.
Pills remaining today is the fill quantity minus the number consumed: days elapsed since fill × daily dose. If the fill date is in the future the calculator shows the full supply. The progress bar tracks how far through the prescription you are, making it easy to see at a glance whether a refill is urgent.
Lead time accounts for the real-world delays in refill processing: insurance authorisation, pharmacist queue, and delivery if applicable. A 7-day lead time is a safe default for most maintenance medications in the US; controlled substances often have stricter fill windows set by law (typically no earlier than 30 days supply minus a few days buffer). Always follow your pharmacy's and insurer's specific refill rules.
Frequently asked questions
Most pharmacies can fill a prescription once 75% of the days supply has elapsed (e.g. after day 22 of a 30-day supply). With a 7-day lead time, requesting on or after day 23 gives the pharmacy a week to process it before you run out. Enter your specific lead time in the calculator to get the exact date.
Days supply is the number of days the dispensed quantity is expected to last at the prescribed dose. It is printed on your label and determines when insurance will pay for a refill. For example, 60 tablets at 2 per day = 30 days supply.
Yes — enter the total doses (puffs, mL, or units) as "total pills" and your daily dose in the same units. For example, an inhaler with 200 puffs used at 2 puffs twice daily (4/day) gives 50 days supply.
Also known as
TG we-Calculate Editorial Team. (2026). Prescription Refill Calculator — When to Refill Your Medication [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/prescription-refill-calculator
TG we-Calculate Editorial Team. "Prescription Refill Calculator — When to Refill Your Medication." TG we-Calculate. 2026. https://we-calculate.com/calculator/prescription-refill-calculator.
TG we-Calculate Editorial Team, "Prescription Refill Calculator — When to Refill Your Medication," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/prescription-refill-calculator
@misc{wecalculate_prescription_refill_calculator, title = {Prescription Refill Calculator — When to Refill Your Medication}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/prescription-refill-calculator}}, year = {2026}, note = {TG we-Calculate} }
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